If I correctly understand you are using Community Edition for this. The difference between community and enterprise version is the fact that Robot service is working under user thread for community version. This means that each task/job will work only when user is logged in.
There is workaround for this but you need to know that it’s not official solution and it might change some day. So you can install robot from MSI package (enterprise installer). This will make a robot running under system thread so you robot will be available anytime no matter if user is logged in or not.